This application is based on and claims the priority under 35 U.S.C. xc2xa7119 of German Patent Application 100 21 520.3, filed on May 3, 2000, the entire disclosure of which is incorporated herein by reference.
The invention relates to a direct drive of a reed in a loom for performing the back and forth beat-up motion. The reed to be driven is mounted on a reed slay which in turn is oscillatable back and forth about a rotational longitudinal axis of a reed support shaft.
There are two types of reed drive. The first reed drive type derives power from the main loom drive. The second reed drive type has its own power source. When the reed driving power is derived from the main loom drive, suitable drive transmission components are required, particularly gear drives that connect the reed support shaft to the main loom drive shaft. In such drives the reed is mounted to the reed support shaft by at least one reed slay. The drive transmission between the main loom drive shaft and the reed support shaft constitutes a rigid coupling. Such rigid coupling in looms which otherwise are representing the most recent state of the art, forms a bottleneck, so to speak, in certain respects because a rigid coupling is not amenable to a rapid, inexpensive change of the tilting angle or angle range of the reed slay and the reed. A rather costly and time consuming effort and expense is necessary when such change in the angle of the beat-up motion is required, for example when changing the loom from weaving smooth fabric to weaving terry cloth and vice versa.
European Patent Publication EP 0,892,100 A1 discloses an apparatus that is capable of changing the angle range of the beat-up motion. However, the extra effort and expense is substantial. The drive of the slay is derived from the main drive of the loom. The slay is mounted for a tiltable oscillating back and forth movement for performing the basic beat-up motion. The main loom drive supplies the power that is transmitted through a transmission (5) to the slay for the basic oscillating motion about a tilting axis. The reed position is adjustable, e.g. the beat-up position is adjustable by a separate servomotor 11. Such adjustment of the beat-up position is desirable, for example for the production of terry cloth. The separate servo-motor (11) and its worm gear transmission (12, 13) constitute an extra effort and expense even if the angular oscillating motion of the reed is derived from the main loom drive.
The second type of reed drive for the oscillating motion is disclosed in European Patent Publication EP 0,440,579 B1 which describes a reed drive that is independent of the main loom drive. The drive system for the reed comprises means for transmitting the variable r.p.m. of an electric motor onto the shaft that carries the slay which in turn carries the reed. The drive motor of this independent drive system requires a closed loop control for varying the motor r.p.m. The transmission of the drive power of the electric motor to the reed support shaft requires drive transmissions such as at least one coupling gear or an eccentric cam drive or a belt drive. All these components require a respective installation space within the loom. Moreover, drive systems of this type are rather prone to wear and tear and hence the maintenance effort and expense is substantial.
German Patent Publication 198 21 094 A1 discloses a loom with a reed that is driven by an electromagnetic linear motor that imposes a controlled back and forth oscillating motion on the reed. For this purpose the slay is connected to the linear motor by an articulated connecting rod, whereby the rod and an electromagnet forms the electromagnetic linear motor for the slay or the reed. Such a drive makes it possible to adjust the beat-up angle of the slay in any desired position independently of the main loom drive. Another advantage is seen in that the beat-up frequency can be adjusted to any particular requirement in a simple manner. However, these advantages have to be considered in the light of substantial disadvantages. The articulated connecting rod constitutes a structural element that has critical characteristics because the articulated connection of the connecting rod to the slay requires a bearing that is exposed to a substantial wear and tear. As a result, maintenance work needs to be done frequently which reduces the productivity of a loom equipped with such an external linear motor. Moreover, if the maintenance work is not performed often enough, a substantial play may develop in the articulating bearing so that the quality of the individual beat-up motions becomes different over time. Such differences in the beat-up motion are quite noticeable in the finished fabric, either in the form of insufficiently dense fabric spots or in extremely dense fabric spots amounting even to stripes in the finished fabric. Another disadvantage of the construction with an external linear motor is seen in that the linear motor must be positioned outside of the slay of the loom, thereby not only increasing space requirements, but also requiring a relatively stiff construction of the connector rod and the stationary component of the linear motor in order to achieve an oscillating motion of the slay and thus of the reed. Another limitation of the external linear motor is seen in that it has its limitations with regard to the high speed capability of modern looms with regard to their r.p.m. and with regard to the weaving width.
In view of the foregoing it is the aim of the invention to achieve the following objects singly or in combination:
to provide a rotary drive for a reed or rather for the slay that carries the reed which drive avoids the drawbacks outlined above while simultaneously accommodating the requirements of modern high speed looms without deriving its driving force from the main loom drive;
to provide a reed drive that is independent of the main loom drive while simultaneously accommodating the performance parameters of modern looms, particularly with regard to high speed r.p.m.s;
to construct the reed drive with a low mass and which shall not require additional installation space in the loom and so that the drive realizes an oscillating dynamic of the reed that is uniform throughout the weaving process from start to finish so that variations in the fabric density are avoided, particularly start-up faults in the fabric are to be avoided;
to provide a reed drive that is suitable for weaving smooth fabrics as well as terry cloth fabrics; and
to permit an adjustment of the oscillating angle and of the beat-up position of the reed to any position within the total oscillating angle of the reed.
The above objects have been achieved according to the invention in that the reed drive has a direct electromagnetic drive motor into which the reed support shaft is integrated as a motor component. The direct drive electromagnetic motor comprises a rotor and a stator. Either the stator or the rotor is formed by the reed support shaft. In a second embodiment the direct drive motor comprises electromagnetic motor elements that together with the reed support shaft form a linear motor. The linear motor elements are angularly arranged around the reed support shaft to form a circular configuration to convert linear motion components of the linear motor into oscillating reed beat-up motions oscillating back and forth between a rear position and a beat-up position.
If the reed support shaft is constructed as a stator, the shaft is mounted in a rigid position in the loom frame and an external rotor surrounds the nonrotatable shaft, whereby the external rotor carries at least one slay which in turn carries the reed.
The direct drive motor in another embodiment is constructed as an electric servomotor or as a circularly configured electromagnetic linear motor. The linear motor also comprises two embodiments, either with the reed support shaft stationary or with the reed support shaft forming the movable component of the linear motor.
With the direct drive constructions according to the invention it is possible to adjust the basic position of the reed angularly to a rotational angle xcex1l within the outer limits of the total oscillating angle xcex12 of the reed, whereby the rotational angle xcex11 is measured relative to the vertical V. The total angular oscillation xcex12 is also variable, but not relative to the vertical.
In another embodiment of the invention the reed support shaft of the loom forms the rotor of at least one electromagnetic direct drive motor for the reed while the stator is rigidly mounted in the machine frame. The functions of the rotor and stator are merely exchanged relative to each other.
It is preferred to provide more than one direct reed drive. For example if two such drives are provided one drive will be positioned at each end of the reed support shaft. If only one drive is provided, such drive may be positioned anywhere along the length of the reed support shaft within the weaving width of the loom. Further, if more than two drives are provided along the weaving width, these drives may be uniformly spaced. Where more than two drives are provided, it is necessary that the component that forms the stator is provided with a segmental recess within the oscillating angular range of the slay. The use of a plurality of direct drives according to the invention is particularly beneficial for looms having a large weaving width since the respective reed support shafts require a larger torque moment for performing the oscillating back and forth beat-up motion.
The embodiment of the linear motor constituting the reed drive according to the invention has its components and elements arranged in radial or rather angular fashion to form a circular configuration, whereby the reed support shaft constitutes a rigidly mounted structural motor component. However, such rigidly mounted component is still referred to as a xe2x80x9cshaftxe2x80x9d even though it does not rotate in this particular embodiment. If the shaft is stationary, the slay is mounted on the stationary shaft through a bearing that is rotatable about the longitudinal central axis of the stationary reed support shaft. The slay has a section between the slay root and the mounting bearing, which section is formed as a segment in such a way that permanent magnets forming motor elements are mounted on one axially facing side of the segment surface areas or on both axially, but oppositely facing, segment surface areas. These permanent magnets form, according to the invention, with the slay the secondary or movable portion of the electromagnetic linear motor. The primary portion of the linear motor is formed by electromagnetic coils which are mounted on a fan-shaped coil support that is rigidly mounted to the reed support shaft forming the stator. The coils are mounted in positions that correspond to the positions of the permanent magnets of the secondary portion of the linear motor. In a preferred embodiment the primary and secondary elements of the linear motor positioned as just described form, according to the invention, a disk armature motor.
According to another embodiment of the invention two linear drive motors are used to cooperate in a push-pull manner so that one drive causes the beat-up motion of the reed while the other drive returns the reed into the rear position.
In order to ascertain the instantaneous angular position of the reed support shaft or the reed within a predetermined angular range xcex12, at least one of the drives is equipped with a signal transmitting synchronous resolver which is connected with the electronic central loom control of the loom to transmit angular position signals to the central loom control.
It is a distinct advantage of the direct reed drives according to the invention that most varied beat-up positions and beat-up forces of the reed can be adjusted relative to the beat-up line of the fabric. A further advantage is seen in that already from the very start of the loom the dynamic of the reed motion is established corresponding to the dynamic that conventionally only develops with a continuous loom operation, whereby from the very start a uniform fabric is produced and so-called start-up faults in the fabric are avoided.